Al—Si alloy, possessing excellent casting property and good mechanical, physical and chemical properties, is the most important series among aluminum-based cast alloys and accounts for 85%-90% of the total yield of aluminum castings. The mechanical property of the cast Al—Si alloy depends on the shape, size and distribution of primary α-Al, eutectic Si, a secondary phase intermetallic compound and pores.
Grain refinement can enhance strength and elongation rate of the aluminum alloy, improve the mechanical property, improve the feeding capacity during solidification, increase the density of the casting, reduce the casting porosity and cracks, improve the distribution of a second phase, and improve the surface smoothness of the casting and the like at the same time.
A traditional grain refinement method is adding Al—Ti—B grain refiner into the aluminum alloy. As the grain size of the cast alloy in a traditional forming mode has reached a limit, it is relatively difficult for the prior refinement method to meet the demands for the high-toughness aluminum alloy in the fields of automobiles, aviation and aerospace. Other methods for obtaining the fine grains, such as rapid solidification and spray deposition have application bottlenecks in the aspect of direct forming of complex parts by casting. Thus, it is one of main difficulties in the development of the high-performance Al—Si alloy to obtain the preparation of the high-toughness Al—Si alloy without reducing the strength.
According to document retrieval, it is found that, by grain refinement, the elongation rate of the ZL101 alloy can be improved from original 3.9% to 6.5% in Zhang Yijie, et al., Influence of Al—Ti—B nano-grain refiner on mechanical and damping properties of ZL101 alloy, Rare Metal Materials and Engineering, 2006, 35(3): 476-479. Although the elongation rate of the Al—Si alloy can be effectively improved through the method, the demands for high toughness (having the elongation rate of more than 12%) in the fields of automobiles, aviation and aerospace are still very difficult to meet.